地震作用下地裂缝场地土体的损伤量化分析∗

Quantitative Analysis of Soil Damage in Ground Fissures Site under Seismic Action

摘要:

为研究地震作用下地裂缝场地的破坏特征和损伤变化规律，以西安 f4 地裂缝场地为背景，进行振动台模型试验。基于希尔伯特边际谱理论，通过土体内部实测数据对地裂缝场地损伤过程进行分析。结果表明：(1)地震作用下，地裂缝场地上、下盘土体变形不一致导致主裂缝两侧产生张拉应力，使得主裂缝不断开裂、扩展，破裂面为锯齿状，且上盘区域产生的次生裂缝更多；(2)损伤指数的发展规律与试验现象较为吻合，说明此损伤量化方法适用于评价地裂缝场地在地震作用下的损伤特征；(3)地表各测点的损伤指数和峰值加速度分布规律表现出较高的一致性，均在靠近地裂缝处达到最大，随着与地裂缝距离的增大而递减，表现出“上、下盘效应”，土体的损伤状况与输入峰值加速度、土层类别等因素有关。

Abstract:

To investigate the damage characteristics and change laws of ground fissures sites under earthquakes， the shaking table model test on soil was designed and completed， based on the ground fissures site of f4 in Xi'an. The damage process of the ground fissures site was analyzed by the mea- sured data in soil， based on the Hilbert margin spectrum. The results showed that：(1)The inconsis- tent deformation of the hanging-wall and footwall of the ground fissures site leads to tensile stress on both sides of the main fissure. Thus， the main fissure gradually cracked and expanded， and the crack surface was in a sawtooth shape. The number of secondary fissures was more than that on the foot- wall.(2)The development law of damage index was consistent with the experimental phenomenon， indicating that the damage quantification method was suitable for detecting the damage development of ground fissures sites under earthquakes.(3)Distribution laws of damage index and peak acceleration on the surface were highly consistent. All parameters reached the maximal value at the fissure， and the peak value gradually decreased from the main fissure to the two sides， showing “hanging-wall/foot- wall effect”. The damage state of soil was related to the input peak acceleration， soil type and other factors.